From patchwork Fri Mar 7 19:45:17 2014
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Date: Fri, 7 Mar 2014 19:45:17 +0000
From: Jonathan Wakely
To: gcc-patches@gcc.gnu.org
Subject: Re: [wwwdocs] Add "Porting to GCC 4.9" document
Message-ID: <20140307194517.GA29739@redhat.com>
References: <20140304223211.GA22968@redhat.com>
<20140307180821.GA15886@redhat.com>
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In-Reply-To: <20140307180821.GA15886@redhat.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
On 07/03/14 18:08 +0000, Jonathan Wakely wrote:
>On 04/03/14 22:32 +0000, Jonathan Wakely wrote:
>>I've added an initial "Porting to GCC 4.9" page at
>>http://gcc.gnu.org/gcc-4.9/porting_to.html
>>
>>So far it only contains a couple of C++ changes that caused some
>>failures during mass rebuilds, other additions are welcome.
>
>The attached patch adds some more changes (thanks to Jakub for the
>OpenMP one) and links to the porting guide form gcc-4.9/changes.html
This patch adds a note about a new warning (thanks to Marek), which
caused some build failures in binutils and gdb.
? .porting_to.html.swp
Index: porting_to.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.9/porting_to.html,v
retrieving revision 1.3
diff -u -r1.3 porting_to.html
--- porting_to.html 7 Mar 2014 19:19:51 -0000 1.3
+++ porting_to.html 7 Mar 2014 19:42:36 -0000
@@ -60,9 +60,32 @@
#pragma omp end declare target
directive, this is now a parsing
error.
-
+
+Right operand of comma operator without effect
+
+GCC now warns about unused right-hand side of a comma expression that
+contains no side effects:
+
+
+ int i = 42;
+ bar (), i;
+
+
+This example now gives the following diagnostic:
+
+
+w.c:5:9: warning: right-hand operand of comma expression has no effect [-Wunused-value]
+ bar (), i;
+ ^
+
+
+To suppress this warning cast the right-hand operand to void
:
+
+
+ int i = 42;
+ bar (), (void) i;
+
C++ language issues